The BGS Lexicon of Named Rock Units — Result Details

Melau Formation

Computer Code: MU Preferred Map Code: notEntered
Status Code: Pending Upgrade
Age range: Llanvirn Series (OE) — Llanvirn Series (OE)
Lithological Description: Mafic agglomeratic tuff, tuffite and thin mafic pillowed lava flows with interbedded silty mudstones.
Definition of Lower Boundary: Conformably overlies the volcaniclastic sandstones of the Allt Lwyd Formation and passes laterally into the undivided siltstones and mudstones of the Aran Volcanic Group; locally, conformably overlies the felsic tuffs of the Offrwm Volcanic Formation.
Definition of Upper Boundary: Conformably overlain by silty mudstones of the Aran Volcanic Group over much of the Harlech district, but locally overstepped by the Benglog Formation with apparent unconformity/disconformity.
Thickness: To 220m
Geographical Limits: Harlech and Bala districts, North Wales.
Parent Unit: Aran Volcanic Group (AVG)
Previous Name(s): Melau Tuff Formation (-4208)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Partial Type Section  River section and adjacent crags in the Afon Melau. Allen, P M and Jackson, A A. 1985. 
Reference(s):
Allen, P M and Jackson, A A. 1985. Geology of the country around Harlech. Memoir of the British Geological Survey, Sheet 135 with part of Sheet 149 [England and Wales]. [London: HMSO.] 112pp. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E136 E135